DENVER – Obese dialysis patients younger than age 65 years were 1.6 times more likely to die within 7 years, compared with their younger, normal-weight dialysis counterparts.
In addition, young and elderly dialysis patients alike who were underweight faced about a twofold increased risk of dying within the same time frame.
The findings come from the Netherlands Cooperative Study on the Adequacy of Dialysis (NECOSAD), a prospective analysis of 1,749 dialysis patients at 38 centers who were at least 18 years old at their first dialysis treatment and were followed until death, transplantation, or a maximum of 7 years.
"Mortality patterns of body mass index differ between young and elderly dialysis patients," Dr. Ellen K. Hoogeveen said during a press briefing Nov. 18 at the annual meeting of the American Society of Nephrology, where the findings were presented. "Obesity may be harmful in patients younger than 65 years. For patients younger than 65 years starting with dialysis, it is important to strive for normal weight."
At baseline, the researchers classified patients into one of two age groups: young (younger than age 65) and elderly (age 65 and older). They also classified them into one of four weight groups based on body mass index: underweight (less than 20 kg/m2), normal weight (20-25 kg/m2), overweight (25-30 kg/m2), and obese (30 kg/m2 or higher). They used Cox regression analysis to calculate hazard ratios associated with BMI categories, and used normal weight as the reference category
Dr. Hoogeveen, of the department of nephrology at Jeroen Bosch Hospital, Den Bosch, the Netherlands, reported that the mean age of the younger patients was 51 years, while the mean age of elderly patients was 73 years. The mean BMI of both groups was 24 kg/m2, and more than half were men (62% in each group).
The 7-year mortality rate for all patients was 67%. When the researchers adjusted for age, gender, smoking, cardiovascular disease, and modality of dialysis, they found that younger patients who were obese at baseline were 1.6 times more likely to die within 7 years than were younger, normal-weight patients. Elderly obese patients were 1.1 times more likely to die within 7 years than were younger, normal-weight patients, a statistically significant difference.
In addition, young and elderly dialysis patients alike who were underweight at baseline were at significantly increased risk of dying within 7 years, compared with younger patients who had a normal BMI (hazard ratios of 2.2 and 1.6, respectively).
One of the study authors, Dr. Elisabeth Boeschoten, is a consultant for Amgen and Baxter and receives grants/research support from Abbott, Amgen, Baxter, Genzyme, Roche, and Shire. All of the other authors reported no relevant financial disclosures.